An electronic system may include one or multiple filters that are used for various aspects of signal processing. For example, a given filter may be used to remove unwanted spectral components and/or enhance desired spectral components. As examples of filters, the electronic system may include a low pass filter that generally passes spectral components having frequencies lower than a cutoff frequency and attenuates spectral components having frequencies greater than the cutoff frequency; a high pass filter that generally passes spectral components having frequencies higher than a cutoff frequency and attenuates spectral components having frequencies lower than the cutoff frequency; a band pass filter that generally passes spectral components having frequencies within a certain continuous band of frequencies and attenuates spectral components otherwise; and so forth.
A given filter may be implemented using either analog or digital signal processing. For a filter that uses analog signal processing, the filter receives a continuous time, or analog, input signal, and the filter contains various analog circuit components (for example, resistors, capacitors and an operational amplifier) to apply the filter's transfer function to the input signal to produce a continuous time output signal. For a filter that uses digital signal processing, discrete time samples that represent time ordered samples of an input signal are numerically processed to apply the filter's transfer function to produce a discrete time output signal.